Optical networks are vulnerable to various types of security threats. In one type of attack, sometimes referred to as a man-in-the-middle (MITM) attack, an intruder severs a fiber connecting two nodes of the network and inserts an intrusion device that intercepts signals communicated across the fiber by the two nodes. To prevent its detection, the intrusion device may regenerate the intercepted signals so that each node continues to receive optical signals from the other node after insertion of the intrusion device in the fiber's path. In this scenario, the intrusion device could remain in the path and, hence, have unauthorized access to communicated data for long periods of time.
As optical networks become a significant element of data transfers for individuals, banks, and other data users, there is a need to protect optical networks from MITM attacks and other security threats. It is generally desirable for the circuitry for protecting optical networks from such threats to be relatively simple and inexpensive without adversely impacting the performance of the optical networks.